1. Field of the Invention
The present invention relates to a desensitizing ink for use in pressure sensitive manifold sheets and more particularly, to a desensitizing ink for use in such pressure sensitive manifold sheets which exhibits no blurring with water, a great versatility in various printings, an improved desensitizing effect and set-off property.
2. Description of Related Art
It has been long recognized that colored images can be produced by a reaction between a colorless electron-donating or proton-withdrawing organic compound (referred to as "coupler" hereinafter) and an electron-withdrawing or proton-donating compound (referred to as "developer" hereinafter). As products making use of this phenomenon in practice, one may mention pressure sensitive copy sheets (see e.g., U.S. Pat. Nos. 2,505,470; 2,505,489; 2,550,471; 2,548,366; 2,712,507; 2,730,456; 2,730,457; 3,418,250; 3,672,935), and thermosensitive copy sheets (see, e.g., Japanese Patent Examined Publication Nos. S.43-4160; S.43-7600; S.45-14039; U.S. Pat. No. 2,939,009). Moreover, a method for producing colored images by applying an ink containing a coupler to a sheet coated with a developer also has been known [German patent application (OLS) No. 1939962].
Developers having the properties as defined above include clays, phenol resins, metal salts of aromatic carboxylic acids and the like.
Generally, in pressure sensitive manifold sheets, a combination of a layer having microcapsules containing said coupler and a developer layer has been used to produce colored images by superimposing one over the other, applying writing or typing pressures to the manifold sheets to collapse the microcapsules whereby the coupler and the developer will come to contact with each other.
Generally, the developers are uniformly coated all over the surface of a support sheet in use. When the developer sheets should have certain parts where desired to have nothing recorded depending on the purpose of the use of pressure sensitive manifold sheets, an attempt has been employed to apply a desensitizing ink containing a desensitizer on parts by a printing machine.
Desensitizing inks to be used for such purpose are described in detail, for example, in U.S. Pat. No. 2,777,780: Japanese Patent Examined Publication Nos. S.44-27255; S.45-21448; S.46-22651; S.46-29546: Japanese Patent Unexamined Publication Laid-Open No. S.47-32915: Japanese Patent Examined Publication Nos. S.47-38201; S.48-4050: Japanese Patent Unexamined Publication Laid-Open No. S.48-6805: Japanese Patent Examined Publication Nos. S.49-4484; S.49-19647; S.49-23008; S.49-23850: Japanese Patent Unexamined Publication Laid-Open Nos. S.49-43708; S.49-72009; S.49-77709; S.49-77710; S.49-15513; S.49-83509; German patent application (OLS) Nos. 2343800; 2359079; 2361856: Japanese Patent Examined Publication No. S.58-38119; Japanese Patent Unexamined Publication Laid-Open Nos. S.63-74681; S.63-41184.
Thus, the printing inks as mentioned above comprise generally desensitizers, pigments such as titanium dioxide, binders, and if necessary, diluents such as organic solvents. However, no desensitizing ink having excellent desensitizing effects on various developers and good off-set property has not been obtained. In addition, the use of desensitizers having a higher water solubility may cause blurring with water, or conversely the use of water insoluble desensitizers may not achieve uniformly printed areas when employed in offset printing. That is, the opposite properties have been imparted.